U.S. patent application number 17/284892 was filed with the patent office on 2021-12-09 for method for managing radio link in multi-carrier environment, and device for same.
The applicant listed for this patent is ELECTRONICS AND TELECOMMUNICATIONS RESeARCH INSTITUTE. Invention is credited to Jae Heung KIM.
Application Number | 20210385896 17/284892 |
Document ID | / |
Family ID | 1000005841271 |
Filed Date | 2021-12-09 |
United States Patent
Application |
20210385896 |
Kind Code |
A1 |
KIM; Jae Heung |
December 9, 2021 |
METHOD FOR MANAGING RADIO LINK IN MULTI-CARRIER ENVIRONMENT, AND
DEVICE FOR SAME
Abstract
A method for operating a terminal for radio link management
includes: receiving from a first cell a connection reconfiguration
message, for configuring carrier aggregation, including
configuration information for a second cell; performing beam and
radio link monitoring for the first and second cells; when a beam
failure for the second cell is detected, performing at least one
from among a procedure of reporting the beam failure to the first
and second cells, a procedure of requesting the recovery of the
beam failure from the first and second cells, and a beam recovery
procedure for the second cell; receiving, from the first or second
cell, a control message in response to the report of the beam
failure, or in response to the beam recovery procedure; and, upon
receiving the control message, determining whether the beam
recovery procedure is successful.
Inventors: |
KIM; Jae Heung; (Daejeon,
KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ELECTRONICS AND TELECOMMUNICATIONS RESeARCH INSTITUTE |
Daejeon |
|
KR |
|
|
Family ID: |
1000005841271 |
Appl. No.: |
17/284892 |
Filed: |
October 24, 2019 |
PCT Filed: |
October 24, 2019 |
PCT NO: |
PCT/KR2019/014035 |
371 Date: |
April 13, 2021 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04W 76/19 20180201;
H04W 36/0027 20130101 |
International
Class: |
H04W 76/19 20060101
H04W076/19; H04W 36/00 20060101 H04W036/00 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 25, 2018 |
KR |
10-2018-0128524 |
Dec 14, 2018 |
KR |
10-2018-0161974 |
Sep 19, 2019 |
KR |
10-2019-0115507 |
Claims
1.-20. (canceled)
21. An operation method of a terminal for beam management and radio
link management, the operation method comprising: receiving, from a
first cell operating as a primary cell (PCell), a connection
reconfiguration message for configuring a carrier aggregation
function including configuration information for a second cell
operating as a secondary cell (SCell); performing beam monitoring
operations for the first cell and the second cell and a radio link
monitoring operation for the first cell; in response to detecting a
beam failure for the second cell, performing a procedure of a beam
failure recovery for the second cell, and reporting the beam
failure recovery to the first cell or the second cell; and in
response to detecting a radio link failure (RLF) for the first
cell, re-establishing a radio link with a third cell, and
performing a procedure of reporting the RLF to the third cell.
22. The operation method of claim 21, wherein the procedure of
reporting the RLF to the third cell includes transmitting a RLF
message to the third cell, the RLF message including at least one
of an identifier of the first cell where the RLF occurred, location
information of the terminal at a time of the occurrence of the RLF,
and information on a time elapsed after the occurrence of the
RLF.
23. The operation method of claim 22, wherein the RLF message is a
radio resource control (RRC) layer message.
24. The operation method of claim 22, wherein the RLF message
further includes information on whether a condition for performing
a random access procedure for beam recovery is satisfied, and the
random access procedure is a non-contention-based random access
procedure.
25. The operation method of claim 22, wherein the location
information includes a latitude and/or a longitude of the
terminal.
26. The operation method of claim 21, wherein the procedure of
reporting the beam failure recovery to the first cell includes
transmitting a medium access control (MAC) message including at
least one of information for identifying a failed beam, information
on a time elapsed from the detection of the beam failure, and
information on a time elapsed from the detection of the beam
failure to completion of the beam failure recovery.
27. The operation method of claim 26, wherein the information of
identifying the failed beam is a transmission configuration
indicator (TCI) state identifier or an identifier of a reference
signal for beam monitoring.
28. The operation method of claim 26, wherein the MAC message is a
MAC control element (CE) message.
29. An operation method of a base station operating a first cell
and a second cell, the first cell being a primary cell (PCell), and
the operation method comprising: transmitting, to a terminal, a
connection reconfiguration message for configuring a carrier
aggregation function including configuration information on the
second cell operating as a secondary cell (SCell); in response to
detecting a beam failure for the second cell at the terminal,
performing a procedure of receiving a report of a beam failure
recovery from the terminal via the first cell or the second cell,
the beam failure recovery being performed by the terminal for the
second cell; and in response to detecting a radio link failure
(RLF) for the first cell at the terminal, performing a procedure of
receiving a report of the RLF from the terminal via a third
cell.
30. The operation method of claim 29, wherein the procedure of
receiving the report of the RLF includes receiving a RLF message
from the terminal via the third cell, the RLF message including at
least one of an identifier of the first cell where the RLF
occurred, location information of the terminal at a time of the
occurrence of the RLF, and information on a time elapsed after the
occurrence of the RLF.
31. The operation method of claim 30, wherein the RLF message is a
radio resource control (RRC) layer message.
32. The operation method of claim 30, wherein the RLF message
further includes information on whether a condition for performing
a random access procedure for beam recovery is satisfied, and the
random access procedure is a non-contention-based random access
procedure.
33. The operation method of claim 30, wherein the location
information includes a latitude and/or a longitude of the
terminal.
34. The operation method of claim 30, wherein the procedure of
receiving the report of the beam failure recovery includes
receiving a medium access control (MAC) message including at least
one of information for identifying a failed beam, information on a
time elapsed from the detection of the beam failure, and
information on a time elapsed from the detection of the beam
failure to completion of the beam failure recovery.
35. The operation method of claim 34, wherein the information of
identifying the failed beam is a transmission configuration
indicator (TCI) state identifier or an identifier of a reference
signal for beam monitoring.
36. The operation method of claim 34, wherein the MAC message is a
MAC control element (CE) message.
Description
TECHNICAL FIELD
[0001] The present invention relates to a method and an apparatus
for radio link management in a multi-carrier environment, and more
particularly, to methods and apparatuses for mobility support and
radio link establishment/management in a mobile communication
system environment supporting carrier aggregation functionality,
which uses a high frequency band above a millimeter wave band.
BACKGROUND ART
[0002] In order to cope with the explosion of wireless data, a
mobile communication system considers a 6 GHz to 90 GHz band as a
transmission frequency for a wide system bandwidth. In such the
high frequency band, it is assumed that a small base station is
used due to deterioration of received signal performance due to
attenuation and reflection of radio waves.
[0003] In order to deploy the mobile communication system based on
small base stations each having a small service coverage,
considering a millimeter frequency band of 6 GHz to 90 GHz band,
instead of implementing radio protocol functions of the mobile
communication system in each small base station, considered is a
method of configuring the mobile communication system by utilizing
a plurality of transmission and reception points (TRPs) through a
functional split scheme, in which the base station functions are
divided into a plurality of remote radio transmission and reception
blocks and one centralized baseband processing function block, or a
carrier aggregation function.
[0004] In the mobile communication system employing such the
functional split or carrier aggregation function, mobility function
support and radio link establishment and management functions are
required to guarantee service continuity in radio interfaces for a
backhaul connecting a base station and a core network, and a
fronthaul connecting the remote radio transmission and reception
blocks (e.g., TRPs, Remote Radio Heads (RRHs), etc.) and the
baseband processing block, as well as an access link between the
base station and terminals.
DISCLOSURE
Technical Problem
[0005] An objective of the present invention for solving the
above-described problem is directed to providing a method for
mobility support and radio link management in a mobile
communication system environment supporting carrier aggregation,
which uses a high frequency band above a millimeter wave band.
[0006] Another objective of the present invention for solving the
above-described problems is directed to providing an apparatus for
mobility support and radio link management in a mobile
communication system environment supporting carrier aggregation,
which uses a high frequency band above a millimeter wave band.
Technical Solution
[0007] An exemplary embodiment of the present invention for
achieving the above-described objective, as an operation method of
a terminal for radio link management, may comprise receiving, from
a first cell operating as a primary cell (PCell), a connection
reconfiguration message for configuring a carrier aggregation
function including configuration information for a second cell
operating as a secondary cell (SCell); performing beam and radio
link monitoring operations for the first cell and the second cell;
in response to detecting a beam problem or failure for the second
cell, performing at least one of a procedure of reporting the beam
problem or failure for the second cell to the first cell and the
second cell, a procedure of requesting recovery of the beam problem
or failure for the second cell to the first cell and the second
cell, and a beam recovery procedure with the second cell; receiving
a control message from the first cell or the second cell in
response to the reporting of the beam problem or failure for the
second cell or in response to the beam recovery procedure; and
determining, according to reception of the control message, whether
the beam recovery procedure is successful.
[0008] The beam problem or failure may be reported to the first
cell and the second cell together with identification information
of a beam from which the beam problem or failure is detected and
information on a time elapsed from a time point when the beam
problem or failure is detected.
[0009] The beam problem or failure may be reported through
transmission of a control field of a physical layer uplink control
channel (PUCCH), transmission of a separate physical layer signal,
or transmission of a random access preamble, which uses an uplink
active bandwidth part (BWP).
[0010] The control field of the PUCCH, the separate physical layer
signal, or the random access preamble may be configured for each of
the first cell and the second cell.
[0011] The beam problem or failure may be directly reported from
the terminal to the first cell, or reported from the terminal to
the first cell through the second cell or another secondary cell
other than the second cell.
[0012] The control message may be received through a control
message of a medium access control (MAC) layer, a control message
of a radio resource control (RRC) layer, a physical layer control
channel, or a random access response (RAR) message.
[0013] The control message may include at least one of information
indicating a change to another beam, information indicating a newly
activated beam, information configuring a new beam, and information
indicating a change of an active BWP.
[0014] The beam recovery procedure may be performed by transmitting
a random access preamble to the first cell or the second cell, or
by transmitting a message for requesting a beam change to the first
cell, another secondary cell capable of receiving uplink
transmission other than the second cell, or the second cell that
has successfully received the random access preamble.
[0015] The random access preamble may be a non-contention-based
random access preamble specified in the connection reconfiguration
message.
[0016] When the random access preamble is a contention-based random
access preamble, a contention-based random access preamble of the
first cell may be preferentially configured as the random access
preamble, or when a random access resource is not configured in an
uplink active BWP, a contention-based random access preamble of a
cell configured as an initial BWP may be preferentially configured
as the random access preamble.
[0017] The random access preamble may be a non-contention-based
random access preamble when a reception strength of a reference
signal or a synchronization signal received through a beam in which
the beam problem or failure is declared is greater than or equal to
a reference value, and the random access preamble may be a
contention-based random access preamble when the reception strength
of the reference signal or the synchronization signal received
through the beam in which the beam problem or failure is declared
is less than a reference value.
[0018] The message for requesting the beam change may be reported
through transmission of a control field of a PUCCH, transmission of
a separate physical layer signal, or transmission of a random
access preamble, which uses an uplink active BWP.
[0019] Another exemplary embodiment of the present invention for
achieving the above-described objective, as an operation method of
a terminal for radio link management, may comprise configuring a
connection with a first cell; determining whether feedback
information or a physical downlink control channel (PDCCH) for
uplink transmission to the first cell is received from the first
cell according to a preconfigured condition; in response to
determining that the feedback information or the PDCCH is not
received according to the preconfigured condition, starting an
uplink polling timer (UL_POLL_TIMER) and transmitting an uplink
polling message to the first cell; in response to receiving an
uplink polling response message or a downlink polling message for
the uplink polling message from the first cell before the uplink
polling timer expires, determining that a beam or radio link with
the first cell is valid; and in response to not receiving the
uplink polling response message or the downlink polling message for
the uplink polling message from the first cell before the uplink
polling timer expires, declaring a failure of the beam or radio
link with the first cell.
[0020] The operation method may further comprise, when the failure
of the beam or radio link with the first cell is declared,
performing a beam recovery procedure with the first cell or
stopping uplink transmission to the first cell for a preconfigured
time.
[0021] The operation method may further comprise, when the failure
of the beam or radio link with the first cell is declared,
reporting the failure of the beam or radio link or requesting
deactivation of the first cell through a second cell.
[0022] Yet another exemplary embodiment of the present invention
for achieving the above-described objective, as an operation method
of a base station operating a primary cell (PCell) for radio link
management, may comprise transmitting, to a terminal, a connection
reconfiguration message for configuring a carrier aggregation
function including configuration information on a second cell
operating as a secondary cell (SCell); in response to detecting a
beam problem or failure for the second cell in the terminal,
performing a procedure of receiving a report of the beam problem or
failure for the second cell from the terminal and/or a procedure of
receiving a request of a beam recovery procedure for the second
cell from the terminal; and transmitting a control message to the
terminal in response to the report of the beam problem or failure
for the second cell or the beam recovery procedure. The beam
problem or failure may be reported from the terminal together with
identification information of a beam from which the beam problem or
failure is detected and information on a time elapsed from a time
point when the beam problem or failure is detected.
[0023] The beam problem or failure may be reported through
transmission of a control field of a physical layer uplink control
channel (PUCCH), transmission of a separate physical layer signal,
or transmission of a random access preamble, which uses an uplink
active bandwidth part (BWP), and the control field of the PUCCH,
the separate physical layer signal, or the random access preamble
may be configured for each of the first cell and the second
cell.
[0024] The beam problem or failure may be directly reported from
the terminal to the first cell, or reported from the terminal to
the first cell through the second cell or another secondary cell
other than the second cell.
[0025] The beam recovery procedure may be performed by receiving a
random access preamble from the terminal, performed by receiving a
message for requesting a beam change from the terminal, or
performed by receiving a message for requesting a beam change
through another secondary cell capable of receiving uplink
transmission of the terminal other than the second cell or the
second cell that has successfully received the random access
preamble.
Advantageous Effects
[0026] According to the exemplary embodiments of the present
invention, in an Xhaul network composed of wireless backhaul and
fronthaul and an access link between the user terminals and the
base station, efficient mobility controls and signaling procedures
for the wireless terminal or user terminal, which is mounted on a
moving object such as an unmanned aerial vehicle, train, autonomous
vehicle, and car using a navigation device, can be provided.
Therefore, in the mobile communication system, mobility support and
radio link management functions for guaranteeing service continuity
can be provided.
DESCRIPTION OF DRAWINGS
[0027] FIG. 1 is a conceptual diagram illustrating a first
exemplary embodiment of a wireless communication network.
[0028] FIG. 2 is a block diagram illustrating a first exemplary
embodiment of a communication node constituting a wireless
communication network.
[0029] FIG. 3 is a conceptual diagram for explaining a structure of
a mobile communication network to which exemplary embodiments of
the present invention are applied.
[0030] FIG. 4 is a conceptual diagram for explaining in more detail
a structure of a mobile communication network to which exemplary
embodiments of the present invention are applied.
[0031] FIG. 5 is a conceptual diagram for explaining an example of
configuring bandwidth parts in a 3GPP NR system to which exemplary
embodiments of the present invention can be applied.
[0032] FIG. 6 is a conceptual diagram for explaining a mobility
support method according to an exemplary embodiment of the present
invention.
[0033] FIG. 7 is a sequence chart for explaining a radio link
management method in a carrier aggregation environment according to
an exemplary embodiment of the present invention.
[0034] FIG. 8 is a sequence chart for explaining a radio link
management method in a carrier aggregation environment according to
another exemplary embodiment of the present invention.
MODES OF THE INVENTION
[0035] While the present invention is susceptible to various
modifications and alternative forms, specific embodiments are shown
by way of example in the drawings and described in detail. It
should be understood, however, that the description is not intended
to limit the present invention to the specific embodiments, but, on
the contrary, the present invention is to cover all modifications,
equivalents, and alternatives that fall within the spirit and scope
of the present invention.
[0036] Although the terms "first," "second," etc. may be used
herein in reference to various elements, such elements should not
be construed as limited by these terms. These terms are only used
to distinguish one element from another. For example, a first
element could be termed a second element, and a second element
could be termed a first element, without departing from the scope
of the present invention. The term "and/or" includes any and all
combinations of one or more of the associated listed items.
[0037] It will be understood that when an element is referred to as
being "connected" or "coupled" to another element, it can be
directly connected or coupled to the other element or intervening
elements may be present. In contrast, when an element is referred
to as being "directly connected" or "directed coupled" to another
element, there are no intervening elements.
[0038] The terminology used herein is for the purpose of describing
particular embodiments only and is not intended to be limiting of
embodiments of the present invention. As used herein, the singular
forms "a," "an," and "the" are intended to include the plural forms
as well, unless the context clearly indicates otherwise. It will be
further understood that the terms "comprises," "comprising,"
"includes," and/or "including," when used herein, specify the
presence of stated features, integers, steps, operations, elements,
parts, and/or combinations thereof, but do not preclude the
presence or addition of one or more other features, integers,
steps, operations, elements, parts, and/or combinations
thereof.
[0039] Unless otherwise defined, all terms (including technical and
scientific terms) used herein have the same meaning as commonly
understood by those of ordinary skill in the art to which the
present invention pertains. It will be further understood that
terms defined in commonly used dictionaries should be interpreted
as having a meaning that is consistent with their meaning in the
context of the related art and will not be interpreted in an
idealized or overly formal sense unless expressly so defined
herein.
[0040] Hereinafter, exemplary embodiments of the present invention
will be described in greater detail with reference to the
accompanying drawings. To facilitate overall understanding of the
present invention, like numbers refer to like elements throughout
the description of the drawings, and description of the same
component will not be reiterated.
[0041] A wireless communication network to which exemplary
embodiments according to the present invention are applied will be
described. The wireless communication network to which exemplary
embodiments according to the present invention are applied is not
restricted to what will be described below. That is, the exemplary
embodiments according to the present invention may be applied to
various wireless communication networks. Here, the wireless
communication network may be used with the same meaning as a
wireless communication system.
[0042] FIG. 1 is a conceptual diagram illustrating a first
exemplary embodiment of a wireless communication network.
[0043] Referring to FIG. 1, a wireless communication network 100
may comprise a plurality of communication nodes 110-1, 110-2,
110-3, 120-1, 120-2, 130-1, 130-2, 130-3, 130-4, 130-5, and 130-6.
Each of the plurality of communication nodes may support at least
one communication protocol. For example, each of the plurality of
communication nodes may support a code division multiple access
(CDMA) based communication protocol, a wideband CDMA (WCDMA) based
communication protocol, a time division multiple access (TDMA)
based communication protocol, a frequency division multiple access
(FDMA) based communication protocol, an orthogonal frequency
division multiplexing (OFDM) based communication protocol, an
orthogonal frequency division multiple access (OFDMA) based
communication protocol, a single carrier FDMA (SC-FDMA) based
communication protocol, a non-orthogonal multiple access (NOMA)
based communication protocol, a space division multiple access
(SDMA) based communication protocol, or the like. Each of the
plurality of communication nodes may have the following
structure.
[0044] FIG. 2 is a block diagram illustrating a first exemplary
embodiment of a communication node constituting a wireless
communication network.
[0045] Referring to FIG. 2, a communication node 200 may comprise
at least one processor 210, a memory 220, and a transceiver 230
connected to the network for performing communications. Also, the
communication node 200 may further comprise an input interface
device 240, an output interface device 250, a storage device 260,
and the like. Each component included in the communication node 200
may communicate with each other as connected through a bus 270.
[0046] The processor 210 may execute a program stored in at least
one of the memory 220 and the storage device 260. The processor 210
may refer to a central processing unit (CPU), a graphics processing
unit (GPU), or a dedicated processor on which methods in accordance
with embodiments of the present disclosure are performed. Each of
the memory 220 and the storage device 260 may be constituted by at
least one of a volatile storage medium and a non-volatile storage
medium. For example, the memory 220 may comprise at least one of
read-only memory (ROM) and random access memory (RAM).
[0047] Referring again to FIG. 1, the wireless communication
network 100 may comprise a plurality of base stations 110-1, 110-2,
110-3, 120-1, and 120-2, and a plurality of user equipments (UEs)
130-1, 130-2, 130-3, 130-4, 130-5, and 130-6. Each of the first
base station 110-1, the second base station 110-2, and the third
base station 110-3 may form a macro cell, and each of the fourth
base station 120-1 and the fifth base station 120-2 may form a
small cell. The fourth base station 120-1, the third UE 130-3, and
the fourth UE 130-4 may belong to cell coverage of the first base
station 110-1. The second UE 130-2, the fourth UE 130-4, and the
fifth UE 130-5 may belong to cell coverage of the second base
station 110-2. Also, the fifth base station 120-2, the fourth UE
130-4, the fifth UE 130-5, and the sixth UE 130-6 may belong to
cell coverage of the third base station 110-3. The first UE 130-1
may belong to cell coverage of the fourth base station 120-1. The
sixth UE 130-6 may belong to cell coverage of the fifth base
station 120-2.
[0048] Here, each of the plurality of base stations 110-1, 110-2,
110-3, 120-1 and 120-2 may refer to a node B (NodeB), an evolved
NodeB (eNB), a base transceiver station (BTS), a radio base
station, a radio transceiver, an access point, an access node, or
the like. Each of the plurality of UEs 130-1, 130-2, 130-3, 130-4,
130-5 and 130-6 may refer to a terminal, an access terminal, a
mobile terminal, a station, a subscriber station, a mobile station,
a portable subscriber station, a node, a device, or the like.
[0049] Each of the plurality of communication nodes 110-1, 110-2,
110-3, 120-1, 120-2, 130-1, 130-2, 130-3, 130-4, 130-5, and 130-6
may support a cellular communication (e.g., long term evolution
(LTE), LTE-A (advanced), etc. defined in the 3rd generation
partnership project (3GPP) standard), or wireless protocol
specifications of mmWave (e.g., 6 GHz to 80 GHz band) based
wireless access technology. Each of the plurality of base stations
110-1, 110-2, 110-3, 120-1, and 120-2 may operate in the same
frequency band or in different frequency bands. The plurality of
base stations 110-1, 110-2, 110-3, 120-1, and 120-2 may be
connected to each other via an ideal backhaul or a non-ideal
backhaul, and exchange information with each other via the ideal or
non-ideal backhaul. Also, each of the plurality of base stations
110-1, 110-2, 110-3, 120-1, and 120-2 may be connected to the core
network (not shown) through the ideal or non-ideal backhaul. Each
of the plurality of base stations 110-1, 110-2, 110-3, 120-1, and
120-2 may transmit a signal received from the core network to the
corresponding UE 130-1, 130-2, 130-3, 130-4, 130-5, or 130-6, and
transmit a signal received from the corresponding UE 130-1, 130-2,
130-3, 130-4, 130-5, or 130-6 to the core network.
[0050] FIG. 3 is a conceptual diagram for explaining a structure of
a mobile communication network to which exemplary embodiments of
the present invention are applied, and FIG. 4 is a conceptual
diagram for explaining in more detail a structure of a mobile
communication network to which exemplary embodiments of the present
invention are applied.
[0051] Referring to FIG. 3, an exemplary embodiment of a method of
connecting a base station and a core network in a mobile
communication network using fronthaul and backhaul is shown. In a
cellular communication network, a base station 310 (or macro base
station) or a small base station 330 may be connected to a
termination node 340 of the core network by a wired backhaul
380.
[0052] Here, the termination node 340 of the core network may be a
Serving Gateway (SGW), a User Plane Function (UPF), a Mobility
Management Entity (MME), an Access and Mobility Function (AMF), or
the like.
[0053] In addition, when base station functions are configured as
split into a baseband processing function block 360 (e.g., a
baseband unit (BBU) or a cloud platform) and a remote radio
transmission and reception node 320 (e.g., a remote radio head
(RRH) or a transmission & reception point (TRP)), the baseband
processing function block 360 and the remote radio transmission and
reception node 320 may be connected through a wired fronthaul
370.
[0054] The baseband processing function block 360 may be located at
the base station 310 that supports a plurality of remote radio
transmission and reception nodes 320 or may be configured as a
logical function between the base station 310 and the termination
node 340 of the core network to support multiple base stations. In
this case, functions of the baseband processing function block 360
may be physically configured independently of the base station 310
and the termination node 340 of the core network, or may be
installed and operated at the base station 310 (or the termination
node 340 of the core network).
[0055] Each of the remote radio transmission and reception nodes
320, 420-1, and 402-2 of FIGS. 3 and 4, and each of the base
stations 110-1, 110-2, 110-3, 120-1, 120-2, 310, 330, 431-3, and
431-4 of FIGS. 1, 3, and 4 may support OFDM, OFDMA, SC-FDMA, or
NOMA based downlink transmission and uplink transmission with
terminals.
[0056] In addition, when the remote radio transmission and
reception nodes of FIGS. 3 and 4 and the plurality of base stations
of FIGS. 1, 3, and 4 support a beamforming function using an
antenna array in a transmission carrier of a mmWave band, services
may be provided without interference between beams within the base
station through the respectively formed beams, and services for a
plurality of terminals (or user equipments (UEs)) may be provided
within one beam.
[0057] In addition, each of the plurality of base stations 110-1,
110-2, 110-3, 120-1, 120-2, 310, 330, 471, and 472 may support a
multi-input multi-output (MIMO) transmission (e.g., a single-user
MIMO (SU-MIMO), a multi-user MIMO (MU-MIMO), a massive MIMO, or the
like), a coordinated multipoint (CoMP) transmission, a carrier
aggregation (CA) transmission, a transmission in unlicensed band, a
device-to-device (D2D) communication (or, proximity services
(ProSe)), or the like. Here, each of the plurality of UEs 130-1,
130-2, 130-3, 130-4, 130-5, 130-6, 410-1, 410-2, 410-3, and 410-4
may perform operations corresponding to the operations of the
plurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2,
and operations supported by the plurality of base stations 110-1,
110-2, 110-3, 120-1, 120-2, 310, 330, 431-3, and 431-4. For
example, the second base station 110-2 may transmit a signal to the
fourth UE 130-4 in the SU-MIMO manner, and the fourth UE 130-4 may
receive the signal from the second base station 110-2 in the
SU-MIMO manner. Alternatively, the second base station 110-2 may
transmit a signal to the fourth UE 130-4 and fifth UE 130-5 in the
MU-MIMO manner, and each of the fourth UE 130-4 and fifth UE 130-5
may receive the signal from the second base station 110-2 in the
MU-MIMO manner. Each of the first base station 110-1, the second
base station 110-2, and the third base station 110-3 may transmit a
signal to the fourth UE 130-4 in the CoMP transmission manner, and
the fourth UE 130-4 may receive the signal from the first base
station 110-1, the second base station 110-2, and the third base
station 110-3 in the CoMP manner. Each of the plurality of base
stations 110-1, 110-2, 110-3, 120-1, and 120-2 may exchange signals
with the corresponding UEs 130-1, 130-2, 130-3, 130-4, 130-5, or
130-6 which belongs to its cell coverage in the CA manner. Each of
the base stations 110-1, 110-2, and 110-3 may coordinate D2D
communications between the fourth UE 130-4 and the fifth UE 130-5,
and thus the fourth UE 130-4 and the fifth UE 130-5 may perform the
D2D communications under coordination of each of the second base
station 110-2 and the third base station 110-3.
[0058] Then, operation methods of communication nodes in a mobile
communication network will be described. Even when a method (e.g.,
transmission or reception of a signal) to be performed in a first
communication node among communication nodes is described, a
corresponding second communication node may perform a method (e.g.,
reception or transmission of the signal) corresponding to the
method performed in the first communication node. That is, when an
operation of a terminal is described, a corresponding base station
may perform an operation corresponding to the operation of the
terminal. Conversely, when an operation of the base station is
described, the corresponding terminal may perform an operation
corresponding to the operation of the base station.
[0059] In the following description, the SGW is a termination node
of a core network for exchanging data packets with a base station
providing services to a user terminal using a radio access
protocol. Also, the MME is an entity in charge of a control
function in a radio access section (or interface) for user
terminals in a wireless communication network. Thus, in the
following description, the present invention is not limited to the
specific terms `SGW` or `MME`. That is, the above-described terms
may be replaced with other terms indicating a function that
supports a radio access protocol according to a radio access
technology (RAT) or an entity that performs the corresponding
function according to a configuration of the core network.
[0060] Referring to FIG. 4, an exemplary embodiment of a
configuration of a radio link between nodes to which functional
split is applied is shown. When the functional split is applied, a
node of a radio access network may be classified into a central
unit (CU) and a distributed unit (DU).
[0061] The CU 432-1 or 432-2 (e.g., gNB-CU in the 3GPP-based NR
systems) is a logical node that controls operations of one or more
DUs and performs radio resource control (RRC), service data
adaptation protocol (SDAP), or packet data convergence protocol
(PDCP) functions according to an RRC protocol and a PDCP
protocol.
[0062] The DU 431-1, 431-2, 431-3, 431-4, 431-5, or 431-6 (e.g.,
gNB-DU in the NR system) may be a logical node that performs
functions of a radio link control (RLC) layer, a medium access
control (MAC) layer, and a PHY layer, or partial functions of the
PHY layer. One DU may support one or more cells, and one cell may
support only one DU. The operation of the DU may be partially
controlled by the CU, and the DU may be connected to the CU through
an F1 interfaces 450-1, 450-2, or 450-3.
[0063] In addition, a DU (e.g., 431-2 or 431-6) for relaying may be
present in a connection section between the DUs 431-1 and 431-4 and
the CUs 432-1 and 432-2 according to configuration, roles, or
properties of the nodes for the functional split. In this case, the
interfaces between the DUs 431-1 and 431-4 and the DUs 431-2 and
431-6 may be connected through relay links 451-1 and 451-2. In
addition, the DU 431 may be connected with the TRPs (or RRHs) 420-1
and 420-2 in a wired or wireless manner, or may be configured as
integrated in the base stations 431-3 and 431-4.
[0064] Meanwhile, in the 3GPP NR system using the millimeter
frequency band, a bandwidth part (BWP) concept is applied to secure
flexibility of channel bandwidth operation for packet transmission.
The base station may configure up to four BWPs having different
bandwidths to the terminal. The BWPs may be configured
independently for downlink and uplink. Each BWP may have not only a
different bandwidth but also a different subcarrier spacing
(SCS).
[0065] FIG. 5 is a conceptual diagram illustrating an example of
configuring bandwidth parts in a 3GPP NR system to which exemplary
embodiments of the present invention can be applied.
[0066] As shown in FIG. 5, a BWP is a bandwidth configured for
transmission and reception of the terminal. The BWPs (i.e., BWP1,
BWP2, BWP3, and BWP4 of FIG. 5) may be configured not to be larger
than a system bandwidth 601 supported by the base station.
[0067] For example, BWP1 is configured with 10 MHz bandwidth having
15 kHz SCS, BWP2 is configured with 40 MHz bandwidth having 15 kHz
SCS, BWP3 is configured with 10 MHz bandwidth having 30 kHz SCS,
and BWP4 is configured with 20 MHz bandwidth having 60 kHz SCS.
[0068] The BWP may be classified into an initial BWP, an active
BWP, or an optional default BWP. The terminal may perform an
initial access procedure with the base station using the initial
BWP. One or more BWPs may be configured through an RRC connection
configuration message, and one of them may be configured as the
active BWP. The terminal and the base station may transmit or
receive data packets using the active BWP among the configured
BWPs, and the terminal may perform a control channel monitoring
operation for packet transmission and reception with respect to the
active BWP.
[0069] In addition, the terminal may switch from the initial BWP to
the active BWP or the default BWP, or may switch from the active
BWP to the initial BWP or the default BWP. Such the BWP switching
may be performed based on an indication of the base station or a
timer. The indication of the base station for switching the BWP may
be transmitted to the terminal using RRC signaling or a DCI of a
physical downlink control channel, and the terminal may switch to
the BWP indicated by the received RRC signaling or DCI. For
example, in the NR system, when an RA resource is not configured in
the active UL BWP, the terminal may switch from the active UL BWP
to the initial UL BWP in order to perform a random access
procedure.
[0070] Mobility Support Method
[0071] FIG. 6 is a conceptual diagram illustrating a mobility
support method according to an exemplary embodiment of the present
invention.
[0072] Referring to FIG. 6, a case in which a beamforming function
is applied between the base station and the terminal is shown. In
the following description, it is assumed that a signal transmitted
by the base station is used to provide an inter-base station
mobility function or to select an optimal beam within the base
station. However, a signal transmitted by the terminal may be used
for the purpose.
[0073] In FIG. 6, the terminal 502-1 or 502-2 may be in a state of
establishing a connection with the base station 501-1, 501-2, or
501-3 and receiving services from the base station, in a state of
establishing a connection with the base station 501-1, 501-2, or
501-3, or in a state of existing within a service coverage of the
corresponding base station without establishing a connection
therewith.
[0074] In a mobile communication system using a base station to
which beamforming techniques are applied in a high frequency band,
a function of changing a beam configured between the base station
and the terminal 502-1 in the base station 501-1, and a mobility
support and radio resource management function of changing beams
configured between the terminal 502-2 and the base stations 501-2
and 501-3 may be considered.
[0075] For example, when a beam #3 of the base station 501-1 and a
beam #2 of the terminal 502-1 are configured (or, beam paired), and
services are provided by the base station 501-1, according to a
change of radio channel quality, the beam used between the base
station 501-1 and the terminal 502-1 may be changed from the beam
#3 of the base station to another beam (e.g., beam #2 or beam #4)
of the base station. Alternatively, the beam used between the base
station 501-1 and the terminal 502-1 may be changed from the beam
#2 of the terminal to another beam (e.g., beam #3, beam #1, or beam
#4) of the terminal.
[0076] Meanwhile, the terminal 502-2, which has configured a beam
with the base station 501-2, may perform a mobility support and
radio resource management function based on a handover procedure,
which changes the beam currently in use to a beam of the adjacent
base station 501-3 according to a change in radio channel
quality.
[0077] In order to perform the mobility support and radio resource
management function, the base station may transmit a
synchronization signal or a reference signal for the terminal to
search or monitor. In case of a base station using a frame format
supporting a plurality of symbol lengths to support
multi-numerology, monitoring by the terminal may be performed for a
synchronization signal or a reference signal configured with an
initial numerology, default numerology, or default symbol
length.
[0078] Here, the initial numerology or the default numerology may
be a configuration of a frame format applied to radio resources in
which a UE-common search space is configured, a frame format
applied to radio resources in which a control resource set
(CORESET) ZERO (or, CORESET #0) of physical downlink control
channels of the 3GPP new radio access technology (New RAT, NR)
system is configured, or a frame format applied to radio resources
through which a synchronization symbol burst for identifying a cell
in the 3GPP NR system is transmitted.
[0079] Here, the frame format may refer to information on
configuration parameters (e.g., values of the configuration
parameters, offset, index, identifier, range, periodicity, or
interval (or, duration), etc.) such as a subcarrier spacing (SCS)
configuring a radio frame (or subframe), a control channel
configuration (e.g., configuration of CORESET), a symbol (or slot)
configuration, a reference signal configuration, or the like. The
information on the frame format may be transferred to the terminal
using system information or a dedicated control message.
[0080] In addition, the terminal, which has configured a connection
with the base station, may perform a beam management operation by
monitoring a configured beam or an activated beam through
transmission of an uplink dedicated reference signal configured by
the base station or reception of a downlink dedicated reference
signal configured by the base station.
[0081] For example, the base station 501-1 may transmit a
synchronization signal (SS) and/or a downlink reference signal so
that terminals in its service coverage can search for itself to
perform downlink synchronization maintenance, beam configuration,
or radio link monitoring operations. Also, the terminal 502-1,
which has configured a connection with the serving base station
501-1, may receive physical layer radio resource configuration
information for connection configuration and radio resource
management from the serving base station.
[0082] Here, the physical layer radio resource configuration
information may mean configuration parameters in RRC control
messages of the LTE or NR system such as PhysicalConfigDedicated,
PhysicalCellGroupConfig, PDCCH-Config, PDCCH-PDCCH-ConfigSIB1,
ConfigCommon, PUCCH-Config, RACH-ConfigCommon,
RACH-ConfigDedicated, RadioResourceConfigCommon,
RadioResourceConfigDedicated, ServingCellConfig,
ServingCellConfigCommon, or the like, and may include the following
information. The configuration information may include parameter
values such as a configuration (or allocation) periodicity of a
corresponding signal (or radio resource) based on a frame format of
a base station (or transmission frequency), position information of
a radio resource for transmission in a time domain/frequency
domain, a transmission (or allocation) time, or the like. Here, the
frame format of the base station (or transmission frequency) may
mean a frame format having a plurality of symbol lengths according
to a plurality of SCS within one radio frame to support
multi-numerology. That is, the number of symbols constituting
mini-slots, slots, and subframes that exist within one radio frame
(e.g., a frame of 10 ms) may be configured differently.
[0083] (1) Configuration information of transmission frequency and
frame format of base station [0084] Transmission frequency
information: information on all transmission carriers (i.e.,
cell-specific transmission frequency) in the base station,
information on BWPs in the base station, information on a
transmission time reference or time difference between transmission
frequencies in the base station (e.g., transmission periodicity or
offset parameter indicating the transmission reference time (or
time difference) of the synchronization signal), etc. [0085] Frame
format information: configuration parameters of a mini-slot, slot,
subframe that supports a plurality of symbol lengths according to
SCS.
[0086] (2) Configuration information of downlink reference signal
(e.g., channel state information-reference signal (CSI-RS), common
reference signal (Common-RS), etc.) [0087] Configuration parameters
such as a transmission periodicity, a transmission position, a code
sequence, or a masking (or scrambling) sequence for a reference
signal commonly applied in the coverage of the base station (or
beam).
[0088] (3) Configuration information of uplink control signal
[0089] Configuration parameters such as a sounding reference signal
(SRS), uplink beam sweeping (or beam monitoring) reference signal
(RS), uplink grant-free radio resources, or uplink radio resources
(or RA preamble) for random access, etc.
[0090] (4) Configuration information of physical downlink control
channel (PDCCH) [0091] Configuration parameters such as a reference
signal for PDCCH demodulation, a beam common reference signal
(e.g., a reference signal that can be received by all terminals in
a beam coverage), a beam sweeping (or beam monitoring) reference
signal, a reference signal for channel estimation, etc.
[0092] (5) Configuration information of physical uplink control
channel (PUCCH) [0093] Scheduling request signal configuration
information [0094] Configuration information for a feedback (ACK or
NACK) transmission resource for supporting HARQ functions, etc.
[0095] Number of antenna ports, antenna array information, beam
configuration or beam index mapping information for application of
beamforming techniques [0096] Configuration information of downlink
and/or uplink signals (or uplink access channel resource) for beam
sweeping (or beam monitoring) [0097] Configuration information of
parameters for beam configuration, beam recovery, beam
reconfiguration, or radio link re-establishment operation, a beam
change operation within the same base station, a reception signal
of a beam triggering handover execution to another base station,
timers controlling the above-described operations, etc.
[0098] In case of a radio frame format that supports a plurality of
symbol lengths for supporting multi-numerology, the configuration
(or allocation) periodicity of the parameter constituting the
above-described information, the time-domain and frequency-domain
position information of the radio resource, or the transmission (or
allocation) time may be information configured for each
corresponding symbol length (or subcarrier spacing).
[0099] In the following description, `Resource-Config information`
may refer to a control message for radio resource configuration
including at least one parameter among the above-described physical
layer radio resource configuration information. In the following
description, a property or setting value (or range) of an
information element (or parameter) transmitted by the corresponding
control message may have a meaning, rather than the name of
`Resource-Config information`. Thus, the information element (or
parameter) conveyed by the Resource-Config control message may be
radio resource configuration information which is commonly applied
to the entire base station (or beam) coverage or dedicatedly
allocated to a specific terminal (or terminal group). The
configuration information of the above-described Resource-Config
information may be configured as one control message or may be
configured as different control messages according to the property
of the configuration information. In addition, the beam index may
be represented without distinction between transmission beam
indexes and reception beam indexes by using an index (or
identifier) of a reference signal mapped or associated with the
corresponding beam, or an index (or identifier) of a transmission
configuration indicator (TCI) state for beam management.
[0100] Therefore, the terminal 502-1 in the connected state may be
provided with services through a beam configured with the base
station 501-1. For example, when the beam #3 of the base station
501-1 and the beam #2 of the terminal 502-1 are configured (or beam
paired) for the terminal to receive services, the terminal 502-1
may search or monitor a downlink radio channel by using a downlink
synchronization signal (e.g., a synchronization signal block (SSB)
of the 3GPP NR system) and a downlink reference signal (e.g.,
CSI-RS of the NR system) of the beam #3 of the base station. Here,
that the beams are configured (or beam paired) and services are
provided may mean that packets are transmitted or received through
an activated beam among one or more configured beams. In the 3GPP
NR system, activation of a beam may mean that a configured TCI
state is activated.
[0101] Through such the radio link monitoring (RLM) operation, the
terminal 502-1 may detect a radio link problem. Here, the detection
of a radio link problem means that there is an error in configuring
or maintaining physical layer synchronization for the corresponding
radio link. That is, this means that it is detected that the
physical layer synchronization of the terminal has not been
maintained for a certain time. When a radio link problem is
detected, a radio link recovery operation may be performed. If the
radio link problem is not recovered, a radio link failure (RLF) may
be declared, and a radio link re-establishment procedure may be
performed.
[0102] A physical layer (Layer 1 or physical layer), Layer 2
functions such as Medium Access Control (MAC), Radio Link Control
(RLC), Packet Data Convergence Protocol (PDCP), etc., or Layer 3
functions such as Radio Resource Control (RRC) of the radio
protocol constituting the radio link may participate in the
procedures such as the detection of a physical layer problem in a
radio link, the radio link recovery, the radio link failure
detection (or declaration), and the radio link re-establishment
according to the radio link monitoring operation.
[0103] The physical layer of the terminal may receive a downlink
synchronization signal and/or a reference signal (RS) to monitor
the radio link. In this case, the reference signal may be a base
station common reference signal (Common RS) or a beam common
reference signal, or a dedicated reference signal allocated to the
terminal (or terminal group). Here, the common reference signal
refers to a reference signal that can be received by all terminals
within the coverage (or service area) of the corresponding base
station or beam to estimate a channel. In addition, the dedicated
reference signal refers to a reference signal that can be received
and used for channel estimation only by a specific terminal or
terminal group within the coverage of the base station or the
beam.
[0104] Therefore, when the base station or the configured beam is
changed, the dedicated reference signal for managing the changed
beam may be changed. This means that a procedure for selecting
another beam from among the beams configured through the
configuration parameters between the base station and the terminal
or changing the configured beam is required. In the 3GPP-based NR
system, changing the beam means that an index of another TCI state
is selected among the indexes (or identifiers) of the configured
TCI states or a new TCI state is configured and changed to an
active state. Configuration information on the common reference
signal may be obtained by the terminal through system information.
Alternatively, in case of a handover in which the base station is
changed or in case of connection reconfiguration, the base station
may transmit the configuration information on the common reference
signal to the terminal through a dedicated control message.
[0105] In order to provide service continuity between the base
station and the terminal, a method in which the terminal provides
services by allocating a plurality of beams to one terminal may be
considered. For example, in FIG. 6, the base station 501-1, 501-2,
or 501-3 may allocate a plurality of beams to the terminal 502-1 or
502-2. That is, the base station 501-1 may allocate the beam #2,
the beam #3, and the beam #4 to the terminal 502-1. Alternatively,
the base station 501-2 may allocate the beam #3 and the beam #4 to
the terminal 502-2.
[0106] In this case, the plurality of beams may be allocated in
consideration of moving speed, moving direction, location
information, radio channel quality, or beam interference of the
corresponding terminal. For example, when the moving speed of the
terminal 502-1 is slow, the base station 501-1 may allocate the
beams #2 and #3 adjacent to each other to the terminal 502-1.
However, when the moving speed of the terminal 502-1 is fast, the
base station 501-1 may allocate the beams #2 and #4 to the terminal
502-1, which are not adjacent to each other and are separated from
each other.
[0107] When the terminal 502-2 moves to the base station 501-3
while receiving services by being allocated the beams #3 and #4
from the base station 501-2, if the base station 501-2 and the base
station 501-3 are base stations belonging to different cells (or
sectors), the terminal 502-2 may perform a handover procedure.
During the handover, the terminal 502-2 may receive information on
the configuration of the beams #1 and #2 of the base station 501-3
from the base station 501-2 through a handover control message.
Meanwhile, the information on the beams #1 and #2 may be obtained
by the base station 501-2 through a procedure in which the terminal
502-2 reports measurement results for the target/neighbor base
station 501-3 to the base station 501-2.
[0108] In this case, the information on configuration of the beams
may include at least one of index information of a transmission or
reception beam configured according to a beam monitoring or beam
measurement result, configuration information (e.g., transmission
power, beamwidth, vertical/horizontal angle, etc.) of the
corresponding beam, transmission or reception timing information
(e.g., index, offset value, or the like of subframe, slot,
mini-slot, symbol, etc.) of the corresponding beam, configuration
information of a reference signal of the corresponding beam, and
sequence information or index information of a reference signal of
the corresponding beam.
[0109] In order to allocate a plurality of beams as described
above, the plurality of beams allocated between the base stations
501-2 and 501-3 and the terminal 502-2, and the moving state
(moving speed, moving direction, location information, etc.) of the
terminal, the beam monitoring and measurement results, etc. may be
reported or transferred as included in a signaling control message
for performing the handover.
[0110] In addition, when the terminal 502-2 moves to the base
station 501-3 while receiving services by being allocated the beams
#3 and #4 from the base station 501-2, if the base station 501-2
and the base station 501-3 are base stations belonging to the same
cell (or sector), an intra-cell transmission node change procedure
may be performed. Here, the base station 501-2 and the base station
501-3 may be nodes (e.g., RRH, TRP, node to which a radio protocol
functional split is applied, etc.) in which the radio protocols
such as physical layer, MAC layer, RLC layer, PDCP layer,
adaptation layer, or RRC layer, which constitute a radio access
network, are partially configured. In this case, the adaptation
layer (e.g., service data adaptation protocol (SDAP) layer of the
NR system) is a layer higher than the PDCP, and performs functions
such as mapping between a QoS flow and a data radio bearer (DRB) or
marking of a QoS flow identifier for downlink (or uplink)
packets.
[0111] As such, in the base stations belonging to the same cell,
when the radio protocol layers for the radio access network are
partially configured excluding the RRC layer, a base station change
procedure from the base station 501-2 to the base station 501-3 for
the terminal 502-2 may be performed through the exchange of control
messages of the MAC layer (e.g., MAC control element (CE) or
control PDU) without exchanging control messages of the RRC
layer.
[0112] That is, which layer of the radio protocol layers is
responsible for generating and transmitting/receiving the control
messages for the base station change may be determined according to
up to which of the radio protocol layers for the radio access
network the corresponding base station (e.g., 501-2 or 501-3 of
FIG. 6) is configured to include.
[0113] For example, if the base station 501-2 and the base station
501-3 are configured to include the MAC layer (or RLC layer), the
control messages for the base station change may be generated at a
higher layer than the MAC layer (or RLC layer), and transmitted or
received between the terminal and the base station, and the MAC
function (or, MAC function and RLC function) of the terminal and
the base station should be newly configured after being reset.
[0114] However, when the base station 501-2 and the base station
501-3 are configured to include only a part of the MAC layer or are
configured only with physical layer functions, the control messages
for the base station change may be generated in the MAC layer, and
transmitted or received between the terminal and the base station,
and the base station change may be performed without resetting the
MAC function of the terminal and the base station.
[0115] When the change of the base station (or transmission node)
described above occurs, information for identifying the
corresponding transmitting base station may be transferred to the
terminal by using a control message of the RRC layer or the MAC
layer, or a physical layer control channel according to
configuration conditions of the radio protocol layers of the base
station (e.g., 501-2, 501-3). In this case, the information for
identifying the transmitting base station (or transmission node)
may include an identifier of the base station (or transmission
node), reference signal information, information on a configured
beam (or configured TCI state), information on a sequence (or
scrambling) identifier for the base station (or transmission node),
or the like.
[0116] The reference signal information may be a radio resource of
a reference signal allocated for each transmitting base station,
sequence information or index information of the reference signal,
or sequence information or index information of a dedicated
reference signal allocated to the terminal. Here, the radio
resource of the reference signal may mean parameters indicating a
symbol position on a time axis at which the reference signal is
transmitted and a relative or absolute subcarrier position on a
frequency axis within a radio resource region such as a frame,
subframe, or slot. Such the parameter may be represented by a
number or the like sequentially assigned to index, symbol, or
subcarrier, which represents a corresponding radio resource element
or radio resource set. Hereinafter, the reference signal
information may refer to the above-described transmission
periodicity, the code sequence or masking (or scrambling) of the
reference signal, the radio resource of the reference signal, index
information, or the like. The reference signal identifier may refer
to a parameter (e.g., resource ID, resource set ID) that can
distinguish the corresponding reference signal information uniquely
among one or more reference signal information.
[0117] The information on the configured beam may be an index (or
identifier) of the configured beam (or configured TCI state),
configuration information of the corresponding beam (e.g.,
transmission power, beamwidth, vertical/horizontal angle, etc.),
transmission or reception timing information (e.g., an index or an
offset value of subframe, slot, mini-slot, symbol, etc.) of the
corresponding beam, or reference signal information or reference
signal identifier information corresponding to the corresponding
beam.
[0118] Accordingly, the terminal may identify a target base station
(or transmission node) to perform a beam monitoring operation, a
radio access operation, or a transmission/reception operation of a
control (or data) packet by using identification information of the
transmitting base station (or transmission node), which the base
station transmits using the control message of the RRC layer or the
MAC layer, or the physical layer control channel.
[0119] In the case where a plurality of beams are configured, the
base station and the terminal may transmit and receive packet
information with all the configured beams, and the number of
downlink beams may be the same as or different from the number of
uplink beams. For example, a plurality of downlink beams from the
base station to the terminal may be configured, and one uplink beam
from the terminal to the base station may be configured.
[0120] Alternatively, when a plurality of beams are configured, the
base station and the terminal may not transmit and receive packet
information with all the configured beams, and some of the
configured plurality of beams may be configured as reserved (or
candidate) beam(s) not for transmitting and receiving packet
information. For example, the configured plurality of beams may be
configured in form of primary beam, secondary beam, or reserved (or
candidate) beam(s). In the NR system, such the configuration of the
plurality of beams may mean that the configured TCI state
identifiers (IDs) are configured in form of primary, secondary, or
reserved.
[0121] For example, the primary beam (e.g., primary TCI state ID)
may mean a beam capable of transmitting and receiving data and
control signaling, and the secondary beam (e.g., secondary TCI
state ID or deactivated TCI state ID) may mean a beam capable of
transmitting and receiving only data packets excluding control
signaling. Here, the exclusion of the control signaling may be
performed by a method of restricting the control signaling of
physical layer, layer 2 (e.g., layer 2 such as MAC, RLC, PDCP,
etc.), or layer 3 (e.g., layer 3 such as RRC, etc.) according to
each layer, a method of partially restricting them according to
functions within the layer, or a method of restricting them
according to the type of the control message. However, the type of
control message may mean a type of control message generated or
transmitted/received according to operational functions of the
radio protocol such as discontinuous transmission/reception
(DRX/DTX) operations, retransmission operations, connection
configuration and management operations, measurement/reporting
operations, operations of a paging procedure, operations of an
access procedure, etc.
[0122] In addition, the reserved (or candidate) beam (e.g.,
reserved TCI sate ID or deactivated TCI state ID) may be limited in
transmission and reception of data or signaling packets. Also, the
reserved (or candidate) beam may be configured as a beam on which
the base station or the terminal performs only beam monitoring
operations for beam matching (or configuration) or performs only
measurement and reporting operations. Accordingly, measurement
results for the reserved (or candidate) beam may be reported using
the primary beam or the secondary beam. The measurement or
reporting on the reserved (or candidate) beam may be performed in
accordance with a related configuration parameter or periodically
or aperiodically in accordance with a determination or event
condition of the terminal. In particular, the report of the results
of measurement or beam monitoring on the reserved (or candidate)
beam may be transmitted using a physical layer control channel,
such as a physical uplink control channel (PUCCH) of the LTE (or
NR) system, or a control message of the MAC layer (e.g., a form
such as MAC control PDU). Here, the result of the beam monitoring
may refer to measurement results of one or more beams (or beam
groups) as results of the beam monitoring (or beam sweeping)
operation on the formed beam of the base station, which is
performed by the terminal.
[0123] Based on the report of results of beam measurement or beam
monitoring, the base station may change the property (e.g., primary
beam, secondary beam, reserved (or candidate) beam, active beam, or
deactivated beam) of the beam (or property of the TCI state). Here,
when the TCI state is changed, the property of the TCI state may be
changed to a primary TCI state, a secondary TCI state, a reserved
(or candidate) TCI state, a configured TCI state, an active TCI
state, a deactivated TCI state, or the like.
[0124] As described above with respect to the property of the TCI
state, a state in which a data packet or control signaling can be
transmitted or received even in a limited manner, such as the
primary TCI state or the secondary TCI state, may be assumed as the
active TCI state or a serving TCI state. Also, a state in which it
is a target of measurement or management, but data packets or
control signaling cannot be transmitted or received, such as the
reserved (or candidate) TCI state, may be assumed as the
deactivated TCI state or configured TCI state.
[0125] The change of the property of the beam (or TCI state) may be
controlled at the RRC layer or the MAC layer. When changing the
property of a beam (or TCI state) at the MAC layer, the MAC layer
may notify the higher layer of the beam property change. In
addition, the change of beam property may be transferred to the
terminal using a control message of the MAC layer or a physical
layer control channel (e.g., a physical downlink control channel
(PDCCH) of the LTE (or NR) system). Here, when the physical layer
control channel is used, the control information may be configured
in form of downlink control information (DCI), uplink control
information (UCI), or a separate indicator (or field information)
of the LTE (or NR) system.
[0126] The terminal may request to change the TCI state property
based on the beam measurement or monitoring results. The control
information or feedback information for requesting the change of
the TCI state property may be transmitted using a physical layer
control channel, a MAC layer control message, or an RRC control
message. The control message, signaling information, or feedback
information for changing the TCI state property may be configured
using at least one or more parameters from the above-described
information on configured beam.
[0127] The property change of the beam (or TCI state) described
above may mean a change from the active beam to the deactivated
beam or reserved (or candidate) beam, or a change from the primary
beam to the secondary beam or reserved (or candidate) beam, or vice
versa. That is, it means that the property of the beam is changed
between the beam properties described above, and the change of beam
property may be performed in the RRC layer or the MAC layer. If
necessary, the beam property change may be performed through
partial cooperation between the RRC layer and the MAC layer.
[0128] In addition, when a plurality of beams are allocated, a beam
for transmitting a physical layer control channel may be configured
and operated. That is, a physical layer control channel may be
transmitted using all the multiple beams (e.g., the primary beam or
the secondary beam) or a physical layer control channel may be
transmitted using only the primary beam.
[0129] Here, the physical layer control channel is a channel such
as PDCCH or PUCCH of the LTE (or NR) system, and may transmit
scheduling information including radio resource element (RE)
allocation and modulation and coding scheme (MCS) information,
channel quality indication (CQI), precoding matrix indicator (PMI),
feedback information such as HARQ ACK/NACK, resource request
information such as scheduling request (SR), beam monitoring result
(or TCI state ID) for supporting beamforming function, measurement
information on active or inactive beams, or the like.
[0130] In case that the physical layer control channel is
transmitted using only a downlink primary beam transmitted from the
base station to the terminal, the feedback information may be
received through the physical layer control channel of the primary
beam or data transmitted through the secondary beam may be
demodulated and decoded using control information obtained through
the physical layer control channel of the primary beam.
[0131] Alternatively, in case that the physical layer control
channel is transmitted using only an uplink primary beam
transmitted from the terminal to the base station, scheduling
request information or feedback control information may be
transmitted through the physical layer control channel of the
primary beam.
[0132] In the case of the multiple beam allocation (or TCI state
configuration) described above, parameters indicating allocated
(or, configured) beam indexes for the multiple beams (or TCI
states), spacing between the allocated beams, or whether or not
contiguous beams are allocated may be transferred through signaling
between the base station and the terminal. Signaling for such the
beam allocation may be configured differently according to a report
from the terminal such as moving speed, moving direction, or
location information of the terminal, or moving state, moving
speed, moving direction, and location information of the terminal,
or the quality of radio channel, which the base station can
recognize or obtain by other means. Here, the quality of radio
channel may refer to a signal quality of a radio channel
represented by a channel state indicator (CSI), a Received Signal
Strength Indicator (RSSI), a Reference Signal Received Power
(RSRP), a Reference Signal Received Quality (RSRQ), or the
like.
[0133] In the above description, the radio resource may be
configured by frequency-axis parameters such as center frequency,
system bandwidth, subcarriers, or the like and time-axis parameters
according to a unit of transmission (or reception) time (or,
periodicity, interval, window) such as radio frame, subframe,
transmission time interval (TTI), slot, mini-slot, symbol, or the
like. Additionally, the radio resource may refer to a resource
occupied for transmission in the radio section by applying a
hopping pattern of the radio resource, a beam forming technique
using multiple antennas (e.g., beam configuration information, beam
index), or a code sequence (or bit sequence or signal sequence). In
case of such the radio resource, the name of the physical layer
channel (or transport channel) may vary according to the type (or
property) of data or control message to be transmitted, uplink,
downlink, sidelink (or side channel), or the like.
[0134] Such the reference signal for beam (or TCI state) or radio
link management may include a synchronization signal such as a
synchronization signal (SS) or a synchronization signal block
(SSB), a channel state information reference signal (CSI-RS), a
phase tracking (PT-RS), a sounding reference signal (SRS), a
demodulation reference signal (DM-RS), or the like. A reference
parameter for reception quality of the reference signal for beam
(or TCI state) or radio link management may be configured as a
parameter such as a measurement unit time, a measurement interval,
a reference value indicating a degree of improved change, a
reference value indicating a degree of deteriorated change, or the
like. The measurement unit time or measurement interval may be
configured as an absolute time reference (e.g., ms, sec, etc.),
transmission timing interval (TTI), a radio channel configuration
such as symbol, slot, (sub)frame, scheduling periodicity, etc., an
operation periodicity of the base station or terminal, or the like.
Also, the reference value representing the degree of change in
reception quality may be configured as an absolute value (dBm) or a
relative value (dB). Also, the reception quality of the reference
signal for beam (or TCI state) or radio link management may be
represented by Reference Signal Received Power (RSRP), Reference
Signal Received Quality (RSRQ), Received Signal Strength Indicator
(RSSI), Signal-to-Noise Ratio (SNR), Signal-to-Interference Ratio
(SIR), or the like.
[0135] Beam Management Procedure
[0136] The measurement or monitoring operation for beam (or TCI
state) or radio link management described above may be performed by
the base station or the terminal. The base station or the terminal
may perform the measurement or monitoring operation according to
the parameters configured for the measurement operation or
monitoring, and the terminal may report measurement results
according to configuration parameters for the measurement
reporting.
[0137] According to the measurement result, when the reception
quality of the reference signal satisfies a predetermined reference
value and/or a preconfigured timer condition, the base station may
determine (or, trigger) deactivation (or activation) or the like of
the beam according to the beam (or radio link) management, beam
switching, or beam blockage situation, and transmit a control
message indicating a related operation to the terminal.
[0138] In addition, when the reception quality of the reference
signal according to the measurement result satisfies the configured
reference value and/or preconfigured timer condition, the terminal
may report the measurement result or may transmit a control message
triggering (or requesting) deactivation (or activation) of the beam
according to the beam (or radio link) management operation, beam
switching (or TCI state ID change or property change), or the beam
blockage situation to the base station.
[0139] The basic operation procedure for the beam (or TCI state)
management through radio link monitoring may include a beam failure
detection (BFD), a beam recovery (BR), or a beam failure recovery
(BFR) request procedure, or the like for the radio link. The
function for determining the beam failure detection or beam
recovery operation and triggering the related procedures, control
signaling, or the like may be performed by the physical layer, the
MAC layer, the RRC layer, or the like in cooperation, or the
related function may be performed by them as partially divided.
[0140] The physical layer of the terminal may estimate whether the
physical layer is kept synchronized (or, quality of a physical
layer control channel) through monitoring of the radio link (or
physical layer channel) and transmit the result to a higher layer.
The estimation result may be transmitted to the higher layer in
form of an in-sync indication (hereinafter referred to as `IS Ind`)
or an out-of-sync indication (hereinafter referred to as `OoS Ind`)
in the corresponding monitoring interval.
[0141] The higher layer of the terminal receiving the IS Ind or OoS
Ind from the physical layer may determine whether or not the radio
link is maintained by counting the number of corresponding
indications continuously received or based on a timer. In case of
the timer-based operation, if the IS Ind is not received again
until a preconfigured timer expires after receiving the OoS Ind,
the beam failure detection (BFD) may be determined (or declared)
for the corresponding radio link.
[0142] Such the detection (or declaration) may be performed at the
MAC layer. For example, the MAC layer of the terminal may determine
that a physical layer problem occurs if the OoS Ind is continuously
received by a preconfigured value `N` or if the IS Ind is not
received from the physical layer until a preconfigured timer (e.g.,
timer for Beam Failure Detection (TBFD)) expires after receiving
the OoS Ind. Here, N is a positive integer, and the timer TBFD
starts when the OoS Ind is received after receiving the IS Ind, and
is reset when the IS Ind is received.
[0143] Alternatively, if the uplink transmission to the base
station does not succeed until a predetermined condition is
satisfied, the terminal may determine (or declare) the beam failure
detection. For example, in case of transmitting through an uplink
grant-free resource or transmitting an uplink resource request
(SR), if feedback information or a response message confirming
successful reception of the corresponding transmission is not
received from the base station even after the transmission is
performed (or attempted) by a preconfigured number of times, the
terminal may determine (or declare) the beam failure detection.
Also, the terminal may determine (or declare) the beam failure
detection even when a control message instructing to adjust a
transmission timer of the uplink physical channel is not received
from the base station before a preconfigured timer expires.
[0144] In case of the beam failure detection (BFD) of the radio
link, the terminal may perform a beam recovery operation. For beam
recovery, the terminal may transmit a physical layer control
channel or reference signal pre-allocated for beam recovery or
perform a random access procedure. Also, such the uplink
transmission for beam recovery may be configured to be repeatedly
transmitted until an associated timer expires, and the related
configuration information may be transmitted in advance to the
terminal using system information or a separate control message.
Here, when performing the beam recovery through a random access
procedure, beam recovery completion or failure may be determined
based on a successful completion condition of the random access
operation or a related timer. Also, when performing the beam
recovery through the transmission of the physical layer control
channel or the reference signal that is pre-allocated for beam
recovery, whether the beam recovery succeeds or fails may be
determined based on a condition or timer (e.g., timer for beam
recovery (TBR)) for determining success or failure of the beam
recovery. The parameter or timer TBR for configuring the reference
condition for determining the beam recovery success or failure may
be configured as a cell-specific parameter or a UE-specific
parameter, and may be notified to the terminal using system
information or a dedicated control message.
[0145] For example, when a random access procedure is performed for
notification of the beam failure detection or the beam recovery
failure or for the beam recovery, a random access resource may be
allocated to the corresponding terminal so as to perform a
non-contention-based random access. Here, the random access
resource may be a configuration parameter for transmitting a
physical random access channel (PRACH), and may include a random
access preamble (i.e., PRACH) index, a PRACH masking parameter, a
preamble format for transmitting the PRACH, a time resource for
transmitting the PRACH, a frequency resource for transmitting the
PRACH, radio resource allocation information for transmitting a
random access response message, a window value or related timer
information for receiving the random access response message, or
the like.
[0146] If the terminal does not receive the corresponding random
access response until a preconfigured timer expires, the terminal
may additionally perform a contention-based random access procedure
for notification of the beam failure detection or beam recovery
failure or for the beam recovery operation.
[0147] Alternatively, when performing the beam recovery operation
by transmitting the physical layer control channel or reference
signal allocated in advance, the terminal may perform the beam
recovery operation by transmitting the corresponding control
information or reference signal according to a preconfigured
parameter (e.g., a timer or the number of transmissions).
[0148] When a result of performing the beam recovery operation does
not satisfy a beam recovery success condition, the MAC layer of the
terminal may report a final beam recovery failure to the RRC layer.
The RRC layer, which has received control information notifying the
beam recovery failure from the MAC layer, may determine a radio
link failure (RLF) due to the beam recovery failure and perform a
radio link re-establishment procedure. In this case, the terminal
may transmit a radio link re-establishment request message by
setting a cause of the RLF to the beam recovery failure or beam
failure.
[0149] Radio Link Management Method in Carrier Aggregation
Environment A carrier aggregation (CA) function refers to a
function in which one terminal configures connections with a
plurality of cells. Through the support of the CA function, the
terminal may transmit or receive signaling packets, traffic data
packets, DCI, UCI, feedback information, or the like through a
physical layer data channel (e.g., physical downlink shared channel
(PDSCH), physical uplink shared channel (PUSCH)) or a physical
layer control channel (e.g., PDCCH, PUCCH) with a plurality of
cells connected to the terminal.
[0150] When the terminal receives services from a plurality of
cells using such the CA function, a primary cell (PCell) and at
least one secondary cell (SCell) may be configured for the
terminal.
[0151] FIG. 7 is a sequence chart for explaining a radio link
management method in a carrier aggregation environment according to
an exemplary embodiment of the present invention.
[0152] Referring to FIG. 7, the base station 702 (i.e., primary
cell) may determine support of the CA function for the terminal 701
(S705). The base station 702 may operate as a primary cell and
exchange signaling messages for connection reconfiguration for
configuring the CA function, which include configuration
information on a secondary cell 703 or 704, with the terminal 701
(S706). In the step S706, the primary cell 702 may transmit, to the
terminal 701, a connection reconfiguration message (i.e., RRC
connection reconfiguration message) including control parameters
for supporting the CA function. In the step S706, the
above-described non-contention-based random access preamble for the
beam failure or beam problem detection report or for the beam
recovery may be configured for one or more BWPs or active BWPs
configured in the terminal in units of a cell supporting the CA
function.
[0153] The terminal 701 receiving the connection reconfiguration
message including the CA configuration parameters for the secondary
cell 703 or 704 from the primary cell may transmit a connection
reconfiguration complete message (e.g., RRC connection
reconfiguration complete message) notifying the successful
reception of the corresponding control message to the primary cell
702. Meanwhile, when the secondary cells are configured on an SCell
group basis, the secondary cell 704 may mean an SCell (i.e., PUCCH
SCell) capable of transmitting PUCCHs among the SCells constituting
the SCell group. That the SCells are configured on a group basis
may mean that the same parameters may be applied to the SCells
belonging to the corresponding SCell group.
[0154] After completing the configuration of the CA function
through the signaling procedure of the step S706, the terminal may
perform beam and radio link monitoring operations for the PCell 702
and the SCells 703 and 704 (S707). In this case, the beam failure
detection and beam recovery operation methods described above may
be applied to a basic beam management operation in each cell. That
is, the beam management operation of the terminal may be
independently performed with respect to the PCell or SCell
according to the method described above.
[0155] In addition to the independent beam management operation,
cells supporting the CA function may be controlled to perform an
additional operation for the beam management operation of the
SCell. For example, when a beam problem or failure of the SCell is
detected according to the beam management operation, the terminal
701 may report the beam failure or beam problem for the SCell, or
may request a beam recovery procedure, or may report that the beam
recovery procedure has been performed or completed to the PCell or
PUCCH SCell before performing the beam failure declaration or the
beam recovery operation or independently of performing the
operation (S708). In this case, information on a time elapsed from
when the beam failure detection is recognized or information on a
time elapsed from the beam problem/failure detection to the beam
recovery completion may be transmitted together with information
for identifying the corresponding beam of the SCell by applying the
above-described configuration parameters. Here, the information for
beam identification may be a TCI state ID or a reference signal
(e.g., SSB, CSI-RS, etc.) identifier for beam monitoring.
[0156] The reporting of the beam problem or failure detection, the
beam recovery request reporting, or the beam recovery completion
reporting in the step S708 may be independently performed by the
terminal 701 to each of the cells 702, 703, or 704 supporting the
CA function. Also, the SCell 703 or 704 that receives a control
message informing the beam problem or failure detection report, the
beam recovery request report, or the beam recovery completion
report from the terminal 701 may transfer the relevant information
to the PCell 702 (S708-1). The control message of the step 708-1
may be transferred using a base station internal control message, a
control message between base stations, or a control message between
functional nodes (e.g., DU or CU of FIG. 4) constituting a base
station (or cell).
[0157] The cell 702, 703, or 704 that receives the control message
informing the beam problem or failure detection report, the beam
recovery request report, or the beam recovery completion report
from the terminal 701 may transmit a response message for the
message of the step S708 to the terminal 701 (S709). The control
message of the step S709 may refer to a control message including
beam reconfiguration information or indicating beam
reconfiguration. Such the control message may be transmitted using
a MAC layer control message, an RRC layer control message, or a
physical layer control channel. Here, the message including the
beam reconfiguration information or indicating the beam
reconfiguration may be composed of one or more of information
indicating a change to another beam, information indicating a newly
activated beam, information for configuring a new beam, or
information indicating a change of an active BWP.
[0158] On the other hand, after performing the step S708 or without
performing the step S708, the terminal 701 may transmit a control
message for beam recovery (e.g., random access preamble or message
requesting beam change) to perform a beam recovery procedure for
the cell in which the beam failure or beam problem is detected
(S710).
[0159] That is, the terminal 701 may report the beam problem or
beam failure detection, request the beam recovery procedure, or
perform the beam recovery procedure by performing only one of the
steps S708 and S710 described above.
[0160] In the step S710, the RA preamble transmitted by the
terminal for beam recovery may be transmitted to the cell (SCell)
in which the beam failure or beam problem has been detected or
transmitted to the PCell (or a cell in which the RA preamble
resource is configured). In addition, the `control message for
requesting beam change` using the control message of the MAC layer,
the control message of the RRC layer, or the physical layer control
channel described above may be transmitted to the cell in which a
beam failure or beam problem is not detected and uplink
transmission is possible (e.g., PCell or PUCCH SCell) or the SCell
in which the aforementioned random access is successful.
[0161] The SCell 703 or 704 receiving the control message for beam
recovery (e.g., random access preamble or message for requesting
beam change) from the terminal 701 may transfer relevant
information to the PCell 702 (S710-1). The control message of the
step S710-1 may be delivered using a base station internal control
message, a control message between base stations, or a control
message between functional nodes constituting a base station (or
cell).
[0162] The cell 702, 703, or 704 that receives the control message
for beam recovery from the terminal 701 may transmit a response
message for the message of the step S710 to the terminal 701
(S711). The cell performing the step S711 may be different
according to the following cases. [0163] Case1: When the PCell 702
or the PUCCH SCell 704 performs the step S711 [0164] Case where the
terminal performs the step S708 and/or S709 with the PCell (or
PUCCH SCell), and the PCell (or PUCCH SCell) transmits a response
message [0165] Case2: When the SCell 703 performs the step S711
[0166] Case where the terminal performs the step S708 and/or S709
with the SCell [0167] Case where the terminal performs the step
S708 and/or S709 with the PCell (or PUCCH SCell), and the PCell (or
PUCCH SCell) transfers the corresponding information to the
SCell
[0168] The control message of the step S711 may refer to a control
message including beam reconfiguration information or indicating
beam reconfiguration. The control message of the step S711 may be
transmitted using a control message of the MAC layer, a control
message of the RRC layer, or a physical layer control channel
including the beam reconfiguration information, or using a random
access response message. Here, the message including the beam
reconfiguration information or indicating the beam reconfiguration
may be composed of one or more of information indicating a change
to another beam, information indicating a newly activated beam,
information for configuring a new beam, or information indicating a
change of an active BWP.
[0169] In performing the steps S708 to S711, the terminal 701 may
perform only one step into which the step S708 and the step S710
are integrated to report the detection of the beam problem or beam
failure, to request the beam recovery, or to perform the beam
recovery procedure. In this case, the base station 702, 703, or 704
may transmit a control message for beam recovery or reconfiguration
to the terminal 701 by performing only one step into which the step
S709 and the step S711 are integrated. The control message for beam
recovery or reconfiguration transmitted by the base station to the
terminal may be transmitted using a MAC layer control message, an
RRC layer control message, or a physical layer control channel as
described in the step S709 or S711, and the corresponding control
message may be information indicating a TCI state ID, a CSI-RS
index, or an SSB index, or information (or indicator) indicating
activation for the corresponding beam.
[0170] In case that the PCell 702 transmits such the control
message, the control message may include information on an
identifier(s) of SCell and/or BWP which is a beam recovery or beam
reconfiguration target.
[0171] The terminal 701, which has performed the reporting of the
beam failure or the beam recovery operation through the step S708
and/or the step S710, may determine whether the recovery has failed
(or succeeded) according to a result of the control message
reception operation of the step S709 and/or the step S711 from the
cell 702, 703, or 704 (S712). Upon detecting or determining the
beam recovery failure or the radio link failure in the step S712,
the terminal 701 may transmit a control message for connection
re-establishment to the cell 702, 703, or 704 (S713).
[0172] When the terminal performs a non-contention-based RA
procedure to perform the step S708 or S710, the terminal may notify
the beam failure detection or the beam recovery failure, or perform
the beam recovery operation through a non-contention-based RA
resource configured in the step S706 for the corresponding
cell.
[0173] When the terminal performs a contention-based random access
procedure to perform the step S708 or step S710, the terminal may
give priority to a contention-based RA resource of the PCell.
Alternatively, when the RA resource is not configured in the uplink
active BWP, the terminal may perform the RA procedure by giving
priority to a contention-based RA resource of the cell configured
as the initial BWP.
[0174] In the CA function supporting environment, the terminal 701
and the base stations 702, 703, or 704 may not necessarily perform
all the steps described in FIG. 7 for the beam management and beam
recovery. In particular, each step from S708 to S713 may be
selectively performed. For example, depending on the configuration
of the system or the base station, the capability of the terminal,
or the service situation, each step of the steps S708 to S713 may
be selectively performed to perform operations and signaling
procedures for the beam management and the beam recovery.
[0175] In addition to the method or procedure using FIG. 7, after
detecting the beam failure for the SCell, the terminal may start a
timer (e.g., the above-described beam recovery timer (T.sub.BR) or
an additional timer (e.g., timer for SCell beam recovery timer
(T.sub.S-BR)) for performing the beam recovery operation for the
SCell, and perform the beam recovery operation before the
corresponding timer expires. Alternatively, the terminal may
transmit a control message informing relevant information to the
PCell when the beam failure is declared after performing the beam
recovery operation for the SCell.
[0176] In the above-described procedure, the control message
transmitted by the terminal to the SCell, the PUCCH SCell, or the
PCell for notification of the beam failure detection or beam
recovery failure of the SCell or for the beam recovery may be
transmitted through an uplink physical layer channel, a MAC control
element (CE), or an RRC control message.
[0177] When the terminal transmits the uplink physical layer
channel to the SCell, the PUCCH SCell, or the PCell for
notification of the beam failure detection or beam recovery failure
of the SCell or for the beam recovery, the terminal may transmit a
control field of the uplink physical layer channel using the uplink
active BWP. Alternatively, an additional physical layer signal
configured for the beam recovery may be transmitted or a random
access procedure may be performed.
[0178] For such the beam recovery operation, the base station
(SCell, PUCCH SCell, or PCell) may transfer, to the terminal,
configuration information such as parameters configuring the
above-described RA resource, the physical layer signal for beam
recovery, or the control field in the PUCCH through the connection
reconfiguration (e.g., RRC connection reconfiguration) message (the
step S706 of FIG. 7) for supporting CA functions. In this case, the
parameters such as the RA resource for beam recovery, the physical
layer signal for beam recovery, or the control field in the PUCCH
may be configured on a SCell, SCell group, or beam basis for one or
more BWPs configured in the terminal or the active BWP. Here, being
configured on a beam basis may mean that it is configured in
association with a reference signal identifier (e.g., an index of
CSI-RS or SSB) for beam measurement (or beam monitoring) or a TCI
state ID.
[0179] Accordingly, when the beam failure detection occurs in a
certain SCell, the terminal may transmit, for the beam recovery,
the above-described RA resource or the physical layer signal, which
is configured on an SCell, SCell group, or beam basis, to the
SCell, PUCCH SCell, or PCell, or transmit the control field in the
PUCCH to the PCell or PUCCH SCell, so that the PCell or PUCCH SCell
can identify the SCell and the serving beam (or active beam) that
is the target of beam recovery.
[0180] In the method in which the terminal transmit the MAC CE (or
MAC control PDU) or the RRC control message (e.g., beam recovery
failure report message, radio link failure (RLF) report message,
radio link re-establishment request message, or the like) to the
SCell, PUCCH SCell, or PCell for notification of the beam failure
detection or the beam recovery failure, or for the beam recovery
(BFR), the corresponding control message may be transmitted as
including at least one of the following information or information
obtained by conditionally combining at least one of the following
information.
[0181] Identifier (or index) of the cell where the beam failure
detection or the beam recovery procedure is performed or the cell
where the RLF occurs [0182] Frequency information of the cell where
the beam failure detection or the beam recovery procedure is
performed or the cell where the RLF occurs [0183] Identifier (or
index) of the BWP where the beam failure detection or the beam
recovery procedure is performed or the BWP where the RLF occurs
[0184] Identifier (or index) of the BWP where the beam failure
detection or the beam recovery procedure is performed or the BWP
where the RLF occurs, information for identifying a target beam or
candidate beam of the beam recovery (or, reconfiguration) (e.g.,
TCI state ID, CSI-RS index, or SSB index) [0185] Identifier (or
index) of the BWP where the beam failure detection or the beam
recovery procedure is performed or the BWP where the RLF occurs,
beam measurement result information (e.g., SINR, SNR, RSRP, RSRQ,
path loss measurement value, etc.)
[0186] Measurement result information (e.g., SINR, SNR, RSRP, RSRQ,
path loss measurement value, etc.) of a candidate beam [0187]
Information on whether the condition for performing
non-contention-based random access is satisfied [0188] Time point
at which the beam failure detection or the radio link failure is
recognized [0189] Information on a time elapsed after a time point
at which the beam recovery procedure is initiated or beam failure
detection (BFD) occurs, or information on the corresponding time
point [0190] Location information of the corresponding terminal at
the time of occurrence of beam failure detection (BFD), radio link
failure, or the like, or at the time at which the corresponding
control message is generated and transmitted (here, the location
information may be geolocation information, such as latitude or
longitude, or measurement result information from which the
location can be estimated)
[0191] For the `location information` transmitted by the terminal,
the base station may transmit control information including at
least one or conditionally combined information from the following
information to the terminal using system information or a separate
control message.
[0192] Timing information for location information measurement (or
estimation) [0193] Reference value for reporting measurement
results [0194] A range of measurement result values and an index
corresponding to each range of the measurement result values [0195]
Reference value for reporting geolocation information (e.g.
latitude/longitude, GPS information, or terminal built-in
positioning sensor information) [0196] Fluctuation width (or
fluctuation range) of the geolocation information and index
information corresponding thereto
[0197] Also, when transmitting the location information
corresponding to any one of the expressions as described above, the
terminal may transmit the location information to the base station
in form of at least one or conditionally combined information from
the following information.
[0198] Information indicating whether the configured reference
value is satisfied [0199] Measurement result information [0200] A
range of measurement result values and an index corresponding to
each range of the measurement result values [0201] Geolocation
information [0202] Fluctuation width (or fluctuation range) of the
geolocation information and index information corresponding
thereto
[0203] In addition, the terminal may transmit control information
for requesting deactivation of the corresponding cell to the SCell,
PUCCH SCell, or PCell. In addition, when the terminal transmits the
beam failure detection or beam recovery failure report, the beam
recovery request, the radio link failure (RLF) report, or the radio
link re-establishment request message through a MAC CE (or MAC
control PDU) or an RRC control message, a logical channel
identifier (LCID) for transmitting the control message may be
designated. That is, by using only the LCID of the MAC header (or
subheader) of the MAC layer control message, it may be identified
that the corresponding MAC CE is control information informing the
beam failure detection or the beam recovery failure, or control
information informing the beam recovery, the beam recovery request,
or the radio link failure report. In addition, when the MAC CE is
configured to include the control parameter information described
above, the corresponding control parameter or message may be
configured to be distinguished using field information of the MAC
subheader.
[0204] In case that the terminal transmits control information such
as the beam failure detection, the beam recovery failure report, or
the radio link failure (RLF) report of the SCell through an uplink
physical layer control channel (PUCCH) or a PUSCH using a PUCCH
format, indication information indicating that the corresponding
situation has occurred, the identifier (or index) of the
corresponding cell, the BWP identifier information, or the like may
be transmitted. In this case, transmitting through the PUSCH using
a PUCCH format may mean transmitting the control information in a
form that can be directly recognized by the physical layer of the
receiving side without involvement of the MAC layer (that is,
without MAC (sub)header). When the control information is
transmitted through the PUCCH, the control information may be
transmitted to the PUCCH SCell or the PCell, and a dedicated PUCCH
resource may be allocated for this purpose. That is, the
corresponding control information may be transmitted using the
PUCCH resource allocated exclusively for the beam failure
detection, the beam recovery failure report, or the radio link
failure (RLF) report of the SCell. If there is no pre-allocated
resource or no available PUCCH resource, the corresponding control
information may be transmitted through a random access procedure.
When a non-contention-based random access procedure is performed,
the corresponding control information may be transmitted in form of
a MAC CE or an RRC control message described above through an
uplink resource scheduled first in the random access procedure. On
the other hand, when a contention-based random access procedure is
performed, after completion of the random access procedure, the
corresponding control information may be transmitted in form of a
MAC CE or an RRC control message described above after completion
of the random access procedure.
[0205] The PCell, that has been reported the beam failure detection
or beam recovery failure or received control information requesting
deactivation of the corresponding cell through the SCell or PUCCH
SCell or from the terminal, may deactivate the corresponding SCell
and transmit to the SCell and/or the terminal a control message
informing that the SCell has been deactivated.
[0206] In addition, the SCell, PUCCH SCell, or PCell receiving the
control message of the above-described uplink physical layer
channel (e.g., PUCCH, PRACH, or PUSCH) from the terminal for beam
recovery of the PCell or SCell may activate the corresponding SCell
in case of successfully finishing the beam recovery procedure, and
transmit, to the terminal, control information informing activation
of the recovered beam by using a downlink physical layer control
channel (e.g., PDCCH) or a MAC CE of the SCell, PUCCH SCell, or
PCell. In this case, the SCell, PUCCH SCell, or PCell may transmit
control information informing activation of one or more TCI state
IDs to the terminal in form of a DCI or a UCI in the PDCCH or a MAC
CE. In addition, if necessary, the SCell, PUCCH SCell, or PCell may
transmit, to the terminal, an RRC control message for reconfiguring
the configured TCI state information or reconfiguring configuration
information of parameters for beam management or beam recovery. In
addition, when using cross-carrier scheduling to transmit a
response message for the beam recovery from the terminal or to
start downlink channel transmission after the beam recovery, the
base station (SCell, PUCCH SCell, or PCell) may transmit an
identifier of the corresponding cell and information for
identifying the activated beam. The cell identifier or the beam
identification information may be a TCI state ID, a CSI-RS index,
an SSB index, or the like, and may be transmitted to the terminal
through a PDCCH or a PDSCH.
[0207] When the terminal detects a beam satisfying the beam
recovery (or configuration) condition by monitoring (or measuring)
beams of the SCell in the beam recovery procedure after the beam
failure detection, the terminal may perform an RA operation to the
SCell by using a random access (RA) preamble resource corresponding
to the beam. In this case, the random access procedure may use the
contention-free random access or the contention-based random access
procedure.
[0208] When the terminal attempts the non-contention-based random
access procedure for beam recovery after the beam failure detection
of the SCell and fails the non-contention-based random access
procedure, or when the reference condition for the
non-contention-based random access is not satisfied, the terminal
may be controlled to perform a contention-based random access
procedure to the SCell or PCell. That is, when a reference signal
reception strength of the corresponding beam is greater than or
equal to a reference value, the non-contention-based random access
procedure may be performed, and when less than the reference value,
the execution of the non-contention-based random access procedure
may be restricted.
[0209] Here, the received signal strength of the reference signal
used as the reference value for performing the non-contention-based
random access may be represented by RSSI, SNR, RSRP, RSRQ, or the
like of the corresponding reference signal (e.g., CSI-RS or
synchronization signal and PBCH block (SSB)).
[0210] In addition, a timer (e.g., Timer_X) that specifies a
duration in which the non-contention-based random access procedure
for beam recovery can be performed may be configured, and the
terminal may be configured to perform a contention-based random
access procedure when the non-contention-based random access
procedure is not successfully completed until the corresponding
timer expires.
[0211] Also, when the terminal performs the contention-based random
access procedure for beam recovery, the terminal may transmit
control information including at least one of an identifier of the
cell in which the beam failure detection or beam recovery procedure
described above is performed, information for identifying the
corresponding beam, measurement result information of the
corresponding beam, measurement result information of the candidate
beam, information on whether or not the condition for performing
the non-contention-based random access is satisfied, control
information requesting deactivation of the corresponding cell,
information on a time elapsed from a time point at which the beam
failure detection is recognized (or a time point of starting the
beam recovery), or information of the corresponding time point. The
candidate beam may refer to a beam which is not configured the
corresponding terminal, but its measurement result satisfies the
preconfigured condition (e.g., a beam whose measurement result such
as RSRP, RSRQ, SINR, etc. is equal to or greater than the reference
condition) as well as a beam configured and deactivated for the
corresponding terminal.
[0212] If the SCell is deactivated during the CA function support,
the parameters configured for the radio link or beam management
operation for the corresponding SCell may be released, stopped, or
reset. In addition, a timer (or a counter value of a timer)
configured for the radio link or beam management operation may be
stopped or suspended, or reset to an initial value, so that the
operation (e.g., timer running operation) of the timer is
controlled to be stopped.
[0213] If the SCell has been deactivated due to the beam failure
detection, when the beam recovery for the SCell is completed
according to the above description, the SCell may be activated. If
the beam recovery completion is not according to the RA procedure
by the terminal to the SCell or transmission of control information
for beam recovery by the terminal, but according to a result of
beam monitoring (or measuring) of the SCell, the terminal may
report the completion of beam recovery for the SCell to the PCell
or the SCell. The control message informing the completion of beam
recovery for the SCell may be configured in form of a MAC CE, and
may be transmitted through an uplink message (e.g., MSG3 in the RA
procedure) transmitted first after transmission of the RA preamble
(PRACH) for random access.
[0214] The PCell that receives the control message indicating the
completion of beam recovery for the SCell from the terminal may
activate the corresponding SCell, and transmit control information
on the activation to the SCell and/or the terminal.
[0215] When the bandwidth part (BWP) scheme introduced in the NR
system is applied to the PCell or the SCell, the following method
should be additionally considered in performing the random access
(RA) operation for beam recovery.
[0216] The terminal may transmit a non-contention-based PRACH
through an uplink BWP in which a non-contention-based RA resource
allocated in advance is configured. A response message (e.g., RA
Response (RAR)) for the PRACH transmitted for beam recovery may be
received through a downlink (DL) BWP corresponding to an uplink
(UL) BWP through the PRACH is transmitted (e.g., DL BWP whose
identifier is identical to that of the corresponding UL BWP) or an
initial DL BWP.
[0217] Upon receiving the PRACH for beam recovery from the
terminal, the PCell or the SCell may transmit an identifier of an
active BWP, an active TCI state ID, information requesting a
measurement report, or the like to the terminal together with the
received PRACH index through a random access response (RAR) message
or a PDCCH. In this case, the identifier of the active BWP may be
downlink and/or uplink BWP identifiers. Also, the information
requesting the measurement report may be composed of one or more
bits. When the information is composed of a single bit, this means
an indicator requesting a measurement result for the configured
reference signal identifier, TCI state ID, and the like. When the
information is composed of a plurality of bits, the corresponding
bit information may indicate a reference signal identifier, a TCI
state ID, or a preconfigured measurement target ID, which is a
measurement target.
[0218] The terminal receiving the RAR message or the related PDCCH
control field for the PRACH transmitted for beam recovery from the
PCell or the SCell may receive necessary information by monitoring
a downlink channel in the downlink BWP, and may perform an uplink
transmission operation in the uplink BWP according to the received
active BWP ID. In addition, when the measurement result report is
requested, the terminal may transmit the measurement result for the
measurement target to the PCell or SCell.
[0219] When the non-contention-based RA operation performed for
beam recovery fails or does not succeed or when the
non-contention-based RA for beam recovery is not configured, the
terminal may perform a contention-based RA operation procedure for
beam recovery of the SCell.
[0220] When the contention-based RA operation procedure is
performed for beam recovery, the terminal may transmit a
contention-based RACH through the active uplink BWP or the
configured uplink BWP of the corresponding SCell in which
contention-based RA resources are configured. However, when the
contention-based RA resources are not configured in the active
uplink BWP or uplink BWP configured for the SCell, the terminal may
transmit a contention-based PRACH through the configured active
uplink BWP, the uplink BWP, or the initial BWP. However, in case
that the terminal performs the contention-based random access
procedure, priority may be given to the contention-based RA
resource of the PCell, or in case that the RA resource is not
configured in the uplink active BWP, the terminal may be configured
to perform the RA procedure by giving priority to the
contention-based RA resource of the cell configured as the initial
BWP.
[0221] The response message (e.g., RAR message) for the
contention-based PRACH transmitted for beam recovery may be
received through a downlink BWP corresponding to the uplink BWP
through which the PRACH is transmitted (e.g., DL BWP having the
same identifier for identifying the BWP). Alternatively, the
terminal may receive the response message for the PRACH through the
initial BWP of the SCell or the PCell.
[0222] Upon receiving the PRACH for beam recovery from the
terminal, the PCell or the SCell may transmit the RA response
message to the terminal. Upon receiving the RA response message,
the terminal may notify the beam failure detection or beam
recovery, or transmit a control field indicating a beam recovery
request, an identifier of the SCell, or beam measurement result
together with its own identifier (e.g., C-RNTI). Here, the beam
measurement result may include a received signal strength (e.g.,
information representing RSSI, RSRP, RSRQ, SIR, SNR, etc.) of the
corresponding reference signal measured, an identifier of the
reference signal, the TCI state ID, or the like. However, the
measurement result may be composed of only the reference signal
identifier or the TCI state ID without the received signal strength
information. In this case, the measurement result may include the
reference signal identifiers or the TCI state IDs in the received
signal strength order (or reverse order).
[0223] In the beam recovery procedure using the random access
described above, the terminal may be configured to report only the
measurement result received above a preconfigured reference value.
In addition, when a related timer (e.g., TBR) expires during the
random access procedure for beam recovery, the radio link failure
(RRF) due to the beam recovery failure described above may be
determined and a radio link re-establishment procedure may be
performed. In this case, the terminal may convert the random access
procedure in progress for beam recovery into the radio link
re-establishment request.
[0224] Therefore, during the non-contention-based RA operation, in
the MSG3 stage (first uplink transmission after PRACH
transmission), the terminal may transmit the radio link
re-establishment message, in which the cause of the RLF is set to
the beam recovery failure or the beam failure, to the base
station.
[0225] Also, in case of performing the contention-based RA
operation, in the MSG5 (i.e., second uplink transmission after
PRACH transmission) stage, the terminal may transmit the radio link
re-establishment message, in which the cause of the RLF failure is
set to the beam recovery failure or beam failure. However, even
when performing the contention-based RA operation, in the MSG3
stage, the terminal may be controlled to transmit the radio link
re-establishment message, in which the cause of the RLF failure is
set to the beam recovery failure or beam failure, together with the
identifier of the terminal.
[0226] In addition, in performing the non-contention-based RA for
beam recovery configured for the terminal, when the
non-contention-based RA is not performed because the RSRP (or RSRQ)
reference value for the non-contention-based PRACH transmission is
not satisfied, the terminal may be controlled to perform a beam
recovery operation using contention-based RA resources if a
preconfigured timer (e.g., Timer_X described above) expires. Here,
not satisfying the RSRP (or RSRQ) reference value means that the
signal quality of PRACH for the RA resource configured for beam
recovery is lower than the reference value for the contention-free
PRACH transmission. However, the signal quality or reference value
of the PRACH means the received signal strength of the reference
signal (e.g., SSB, CSI-RS, etc.) that can be expressed by the
above-described RSSI, SNR, RSRP, or RSRQ.
[0227] If necessary, the base station may configure the terminal
having not performed the contention-based RA to perform a beam
recovery operation by using a contention-based RA resource
regardless of the Timer_X operation. In this case, the terminal may
perform the beam recovery operation by transmitting a PRACH using a
contention-based RA resource according to its own decision or when
a preconfigured condition is satisfied.
[0228] In addition, when performing the non-contention-based RA
procedure configured to the terminal for beam recovery or other
purposes, Timer_X may be started (or restarted) at the time when
the terminal triggers the non-contention-based RA procedure. Here,
Timer_X means a timer configured for the terminal to wait without
stopping or canceling the non-contention-based RA procedure until
the corresponding Timer_X expires when the reference value for
performing the non-contention-based PRACH transmission using the
corresponding RA resource is not satisfied. That is, after Timer_X
is started (or restarted), the terminal may performing measurement
or monitoring on whether the reference signal for measuring the
PRACH quality of the non-contention-based RA resource is above (or
below) the reference value before the corresponding Timer_X
expires. In addition, if the reference value condition of the PRACH
quality is not satisfied, the terminal may not perform the
non-contention-based RA operation and may not switch to the
contention-based RA procedure until Timer_X expires. If the
corresponding Timer_X expires while not satisfying the reference
value for the non-contention-based PRACH transmission, the terminal
may transmit the contention-based PRACH by switching to the
contention-based RA procedure or by changing to another BWP.
[0229] In addition to the above-described operation or procedure
for beam failure detection or beam recovery, a signaling (e.g.,
polling or probing) procedure for estimating a beam state and
determining whether packet transmission and reception are possible
may be performed between the terminal and the base station (serving
cell (or node) such as SCell, PUCCH SCell, or PCell).
[0230] FIG. 8 is a sequence chart for explaining a radio link
management method in a carrier aggregation environment according to
another exemplary embodiment of the present invention.
[0231] In FIG. 8, for convenience of description, an operation of a
single cell of the base station 802 and the terminal 801 is
described. However, the operation of the base station 802 and the
terminal 801 to be described later may also be applied to a carrier
aggregation environment where a plurality of cells (carriers) are
aggregated.
[0232] The base station 802 may configure a first cell and
configure a connection between the first cell and the terminal 801
to provide services (S803). In this case, when the carrier
aggregation function is applied, the terminal 801 may receive
configuration information on one or more secondary cells (e.g., the
second cell) from the primary cell (e.g., the first cell) to
perform the carrier aggregation function.
[0233] The terminal 801 may perform a monitoring operation on the
beam using a reference signal of a downlink channel of the first
cell and perform a reception operation on the downlink channel
(S804). In addition, the base station 802 may perform beam
monitoring using a reference signal of an uplink channel from the
terminal 801 through the first cell, and perform a reception
operation on the uplink channel (S804).
[0234] The terminal 801 may monitor the signal quality of the
downlink channel through the operation of the step S804, and
monitor whether downlink feedback information (e.g., HARQ ACK/NACK
or other control signal) or a physical layer control channel
(PDCCH) for its uplink transmission is received from the first cell
while satisfying a preconfigured condition. Also, the base station
802 may monitor the signal quality of the uplink channel from the
terminal through the operation of the step S805, and may monitor
whether uplink feedback information (e.g., HARQ ACK/NACK) or other
control signal) or a physical layer control channel (PUCCH) for the
downlink transmission through the first cell is received from the
terminal while satisfying a preconfigured condition.
[0235] When a result of performing the step S804 or S805 does not
meet the preconfigured condition, the base station 802 or the
terminal 801 may independently transmit a polling message. Here,
the polling message may be transmitted as configured in a control
field (or bit) of a physical layer control channel (e.g., PDCCH or
PUCCH) or in form of a MAC CE.
[0236] For example, the base station 802 may determine to transmit
a DL polling message through the step S805. In the step S805, the
base station 802 may start a timer (e.g., DL_POLL_TIMER) for a
polling operation, and generate and transmit a DL polling message
through the first cell (S806). The terminal 801 receiving the DL
polling message of the step S806 may transmit a DL polling response
message or generate and transmit a UL polling message (S807).
[0237] Before the DL_POLL_TIMER started in the step S805 expires,
if the base station 802 receives the DL polling response message or
the UL polling message from the terminal 801 through the first
cell, the base station 802 may determine that the corresponding
beam (or radio link) is valid, and continue services using the
corresponding beam (or radio link). On the other hand, if the DL
polling response message or the UL polling message is not received
from the terminal 801 through the first cell and the DL_POLL_TIMER
expires, the base station 802 may declare a beam (or radio link)
failure between the first cell and the terminal, and trigger a beam
recovery procedure or stop the downlink transmission for a
preconfigured time interval (or timer). In addition, when the CA
function is configured, the base station may deactivate the first
cell.
[0238] In addition, in response to the DL polling message in the
step S806, the terminal 801 may transmit a DL polling response
message, or generate a UL polling message and transmit the UL
polling message to the base station 802 through the first cell
(S807). That is, even when there is not the step S806, the terminal
may trigger the UL polling message transmission based on the result
of the step S804. The terminal 801 that triggers the UL polling
message transmission may start UL_POLL_TIMER and generate and
transmit the UL polling message.
[0239] The base station 802 receiving the UL polling message from
the terminal 801 through the first cell may transmit a UL polling
response message (S808). If the base station 802 receives the UL
polling message of the step S807 without the step S806, the base
station 802 may generate and transmit a DL polling message in
response to the UL polling instead of the UL polling response
message.
[0240] When the UL polling response message or the UL polling
message is received from the base station 802 through the first
cell before the UL_POLL_TIMER started in the step S807 expires, the
terminal 801 may determines that a beam (or radio link) between the
first cell and the terminal is valid, and continue services by
using the corresponding beam (or radio link).
[0241] However, when the UL polling response message or the DL
polling message from the base station 802 is not received through
the first cell and UL_POLL_TIMER expires, the terminal 801 may
declare a beam (or radio link) failure between the terminal and the
first cell, and trigger a beam recovery procedure or stop uplink
transmission for a preconfigured time interval (or timer) (S809).
In addition, when the CA function is configured, the terminal 801
may report the beam failure for the first cell or request
deactivation of the first cell through another serving cell (e.g.,
the second cell).
[0242] The polling response message described above may be
transmitted as configured in a control field (or bit) of a physical
layer control channel (e.g., PDCCH or PUCCH) or in form of a MAC
CE.
[0243] The configuration parameter information on the timer value,
the reference value, or the conditions required in the operation or
procedure for beam failure detection or beam recovery described
above may be transmitted by the base station to the terminal
through system information or a separate control message.
[0244] In addition, in the above description, the operation of the
base station (or cell) may be an operation performed by a node such
as CU or DU described with reference to FIG. 4 when the functional
split function is applied.
[0245] With respect to the operation of the timer defined or
described in the present invention, although operations such as
start, stop, reset, restart, or expire of the defined timer are not
separately described, they mean or include the operations of the
corresponding timer or a counter for the corresponding timer.
[0246] The cell (or base station) of the present invention may
refer to a road side unit (RSU), a radio remote head (RRH), a
transmission point (TP), a transmission and reception point (TRP),
or a gNB, in addition to the NodeB, the evolved NodeB, the base
transceiver station (BTS), the radio base station, the radio
transceiver, the access point, or the access node as the base
station described in FIG. 1. It may also be referred to as a CU
node or a DU node according to application of the functional split
described in FIG. 4.
[0247] Also, the terminal of the present invention may refer to an
Internet of Thing (IoT) device, a mounted module/device/terminal,
or an on board device/terminal, in addition to the terminal, the
access terminal, the mobile terminal, the station, the subscriber
station, the mobile station, the mobile subscriber station, the
node, or the device as the UE described in FIG. 1.
[0248] The exemplary embodiments of the present disclosure may be
implemented as program instructions executable by a variety of
computers and recorded on a computer readable medium. The computer
readable medium may include a program instruction, a data file, a
data structure, or a combination thereof. The program instructions
recorded on the computer readable medium may be designed and
configured specifically for the present disclosure or can be
publicly known and available to those who are skilled in the field
of computer software.
[0249] Examples of the computer readable medium may include a
hardware device such as ROM, RAM, and flash memory, which are
specifically configured to store and execute the program
instructions. Examples of the program instructions include machine
codes made by, for example, a compiler, as well as high-level
language codes executable by a computer, using an interpreter. The
above exemplary hardware device can be configured to operate as at
least one software module in order to perform the embodiments of
the present disclosure, and vice versa.
[0250] While the embodiments of the present disclosure and their
advantages have been described in detail, it should be understood
that various changes, substitutions and alterations may be made
herein without departing from the scope of the present
disclosure.
* * * * *